Bags, such as made in accordance with my earlier patent application No. 127,064 filed Mar. 4, 1980, are normally delivered to the consumer in so-called blocks. Such a block is a stack of bags which are adhered together so that the stack can be handled easily. The bags can be ripped one after the other off the block much like sheets of paper from a pad.
A standard apparatus for forming such blocks or pad-stacked bags is described in German Patent Document No. 2,500,964. Such an arrangement has a conveyor divided at a stacking location into an upstream stretch which delivers the flattened-out bags or sheet workpieces one at a time to the location and a downstream stretch which carries away stacks of bags. A pair of drums flank this location. One of the drums is provided with an axially extending array of needles which are directed slightly forwardly in the direction of rotation of the drum and the other drum is provided with a complementarily grooved pusher bar. The two drums are rotated at the same peripheral speed, which is the same as the transport speed for the conveyor, and the operation is so synchronized that the needles poke through the leading end of each bag as it arrives at the location. The needles are rather long so that as the stacker drum having these needles rotates it can pick up a small stack of the bags. Periodically a stripper element pushes all of these bars off the drum so that they can be carried away by the downstream conveyor stretch. Somewhere along this downstream conveyor stretch a soldering tool or the like is provided which welds together the bags of an individual stack at several different locations so as to form the above-described block or pad.
The principal disadvantage of this system is that the bags in the stacks formed by the stacker drum frequently shift somewhat relative to one another during their transport to the blocking or welding location. The only way to avoid this shifting is to operate at relatively low speed, a method which obviously cuts down productivity.